A rotary actuator driven by working fluid such as air includes a vane type rotary actuator, in which vanes are assembled to a rotary shaft accommodated in a cylindrical housing so that the rotary shaft can be rotated by supplying the working fluid to the housing, and a piston type rotary actuator, in which a linear motion of a piston actuated by supplying the working fluid to a cylinder chamber is converted to a rotary motion by a conversion mechanism.
The piston type rotary actuator includes a rack-and-pinion type rotary actuator, in which a rack and a pinion are incorporated as a mechanism that converts the linear motion to the rotary motion (for example, see Patent Document 1). This rack-and-pinion type rotary actuator is widely used in various applications since, for example, its region where the working fluid leaks out is few in number and its durability is high.
The rack-and-pinion type rotary actuator has two cylinder chambers, which are parallel to each other, and pistons are reciprocably accommodated in the respective cylinder chambers. The respective pistons are provided with racks, and, between the racks opposed to each other, a pinion meshing with both of the racks is provided on a shaft part integrated with the table. The working fluid is alternately supplied to both of the cylinder chambers, and the respective racks are caused to reciprocate in opposite directions, whereby the table can be reciprocably swung within a predetermined angle range.
As described in Patent Document 1, to the shaft part of the pinion, a bearing fitted in the housing are assembled, and the table, on which a workpiece, and a jig, etc. are mounted and which drives them, is coupled. When the working fluid is alternately supplied to both of the cylinder chambers in a state in which the jig etc. is attached to the table, a predetermined operation can be performed by rotating the workpiece, and jig, etc.    Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2002-130208